This invention relates to a stirring apparatus and its method of use.
Processes are known in which materials are stirred within a vessel. In particular, numerous chemical processes, such as chemical reactions, involve stirring of reactants together to produce products, which are discharged from the vessel (reactor). For solids, liquids, slurries etc, discharge of material from the vessel may be achieved by allowing the material to flow through a suitable conduit. Where it is desired for the vessel to be completely emptied of material as effectively as possible, the conduit is preferably located at the lowest point (base) of the vessel.
To prevent material from flowing from the vessel when not required the conduit will normally comprise a valve or other sealing means. However, it is often not possible or desirable for the valve to be located on the conduit at a position close to the vessel. For example, the vessel may be heated, for example, by being located in a suitable heated enclosure, such as an oven or a furnace. It may be desirable to have the valve outside that heated area so that it can be readily accessed by an operator and/or so that the valve does not itself get too hot.
Where the valve is located at a distance away from the vessel there is thus a significant length of conduit between the valve and the vessel. Material in the vessel may settle out from the vessel into said conduit. In addition, the longer the conduit, the more likely the conduit is to become blocked, which can cause problems with discharge of materials from the apparatus. This is particularly true where solids or slurries are present in a vessel, for example as reaction products, since such products are often difficult to remove from a vessel. There is a need for a stirring apparatus which overcomes or at least mitigates these problems.
U.S. Pat. No. 4,690,804 relates to catalytic reactions. In particular, U.S. Pat. No. 4,690,804 relates to a mixing tank for catalyst to be introduced into a reactor. The mixing tank has a cylindrical outlet conduit at the base of the tank, and an agitator on a shaft within the tank which terminates in a spiral configuration located within the outlet conduit. The agitator of U.S. Pat. No. 4,690,804 provides agitation within the conduit, preventing bridging of the outlet conduit as catalyst is passed through the conduit from the mixing tank and into a receiver (reaction) vessel below. However, there is no disclosure that the agitator of U.S. Pat. No. 4,690,804 is adapted to convey material within the conduit out of the mixing tank. In contrast, during feeding of catalyst from the mixing tank into the receiving vessel, the flow of catalyst is controlled by a ball-check feed valve, the agitator simply helping to prevent bridging. In addition, there is no disclosure that the agitator of U.S. Pat. No. 4,690,804 is adapted to convey material within the conduit into the mixing tank above.